The objectives of the proposed research are to define factors that contribute to the initiation of transient postoperative ileus following celiotomy. Postoperative ileus is responsible for significant patient discomfort and prolongation of hospitalization following abdominal surgery, and as such has important medical and economic consequences. Defining the factors initiating postoperative ileus is an essential step in understanding the pathophysiology of this process. To date these factors are unknown. The recent use of laparoscopic techniques to perform abdominal operations has been associated with the observation of a marked decrease in severity and duration of postoperative pain and ileus in patients undergoing such procedures. The proposed research will quantitate the degree of ileus following laparoscopic surgical procedures, and compare it to similar open abdominal procedures. Measurement of gastrointestinal myoelectric activity will be the main parameter used to quantitate motility, with confirmation by data from pressure probes, radionuclide emptying studies, and transit studies. Individual factors likely to initiate postoperative ileus, especially those which result in increased trauma and postoperative pain, will be studied in a controlled fashion to determine their contributions to the process. Such factors will include size and depth of abdominal wall incision, bowel or bowel mesentery manipulation, temperature of the operative environment, intestinal or visceral cutting, and the systemic processes of circulating vasopressin, chemical peritonitis, and bacterial peritonitis. Human subjects will be used in the study as appropriate and feasible. Those parts of the study requiring more extensive manipulations will use dogs. Identification of factors initiating postoperative ileus should clarify previously proposed but not confirmed mechanisms by which this process, and perhaps other more sustained pathophysiologic diseases of gastrointestinal motility, are mediated. Knowledge of such mechanisms is needed to direct appropriate future therapy for these disorders.